Sri Lanka has opened up by now. That is fully vaxxed people do not need to quarantine anymore. Not even for one day. You do need a PCR test taken 72 hours before your flight. You need to apply for an ETA (visa online) and will get 30 days, which you can extent later in the country. You need your vaccine certificate. Any vaccine which is accepted in the country of origin, is accepted in SL. And you need to fill in a Health Declaration form. Also online. It has a QR code. But you do that last (I think) because you need your flight details. Oh, and you need a return ticket, or at least a ticket OUT of SL.
Sri Lanka is "doable" at the moment for fully vaxxed people. Mexico is wide open. No need for anything Covid related. Not even need for applying for a visa. You get 180 days on arrival at the airport. And yes, we all want India to open up again :)