Since you've explicitly asked about digital payment options, you have only have a couple of options
- Use UPI one world for foreign tourists
- Get an Indian bank account and use UPI like a local
- Use your foreign issued credit/debit card
You'll hear a lot about how great UPI is, but the reality for foreign tourists or non resident Indian's is that UPI is a PITA. It's not designed to be interoperable with any other global payment system and onboarding is difficult for non residents.
UPI PPI for foreigners
In theory, you can use UPI as a foreign tourist as well. You need to setup a prepaid payment instrument, the directions around this are pretty spotty but there are two providers IDFC First Bank and Cheq which are known to support this. If you want to use this, then your best bet is to find the kiosks of these providers at the Airport where you arrive and then have this setup. This allows you to setup a UPI prepaid wallet on your phone, with which you can make transactions. There are restrictions on how you can load money onto this wallet, i.e. you can't receive funds from Indian domiciled accounts. The other drawback is that you need to know how much money you want to load onto your wallet ahead of time, you also pay uncompetitive rates on FX transfers compared to using your credit/debit card for payments directly. This is a great option if you can get this to work.
Open a local bank account
This is an option to consider only if you're visiting India for a relatively long period of time, 30 days or more. I'm not going to be recommending any particular bank but as a tourist you'll do yourself a favour by staying away from the public sector banks as they're not known for their customer service. Private sector banks have better customer service but are known to try and upsell or sell you junk products.
You can open a NRO account
Q5. What are the accounts that a tourist visiting India can open?
Answer: An NRO (current/ savings) account can be opened by a foreign
national of non-Indian origin visiting India, with funds remitted from
outside India through banking channel or by sale of foreign exchange
brought by him to India. The balance in the NRO account may be paid to
the account holder at the time of his departure from India provided
the account has been maintained for a period not exceeding six months
and the account has not been credited with any local funds, other than
interest accrued thereon.
You can fund this account with either foreign currency in cash, wire transfer or by using any third party remittance service.
With this account, you can transact like a local by using UPI. You still won't be able to use apps like Google Pay for UPI and will have to rely on the bank's own app for UPI. This is because the third party UPI app providers need to do their own KYC, which you will likely not have the documents for.
This option isn't for everyone, but if you do make the effort then it's well worth it, especially for longer trips or if you plan on coming back to India from time to time.
Use your foreign Credit/Debit Cards
If you are in India for a short trip and only going to visit medium to large sized establishments, then you can simply use your foreign issued credit/debit cards. Having a no FX fee credit card is particularly handy and you can use your Debit Card to withdraw cash for smaller transactions. For most tourists, visiting for a short duration, this is going to be the best strategy.