Is alcohol expensive in Singapore?

Yes. A single pint of beer can cost $15-20 SGD at a bar. If you want to drink, buy it at a supermarket (7-Eleven or FairPrice) and drink it in your room, though even then, it is heavily taxed.

Are there free things to do at night?

Yes. The Spectra light show at Marina Bay Sands and the Garden Rhapsody light show at the Supertree Grove are both free and happen every night.

Should I buy a SIM card?

If you want to save, don't. Use free public Wi-Fi available at almost all malls, MRT stations, and public buildings. If you need data, get an eSim like Airalo for about $10 USD.

How to visit Singapore on a budget

Stick to hawker centers for every meal, take public transport exclusively, and fill your itinerary with free nature walks and public cultural sites. Avoid alcohol and taxis, as these will destroy your budget within 24 hours.

Use the MRT and buses. Do not take taxis or Grab. Buy a Singapore Tourist Pass if you are staying for 3 days or more, or simply tap your contactless credit card at the gantries. The MRT reaches every major tourist site for under $2.00 SGD per ride.
Eat at Hawker Centers. Avoid 'restaurants' in malls. Head to stalls in places like Maxwell Food Centre, Old Airport Road, or Tiong Bahru Market. A full meal with a drink will cost you $6-9 SGD.
Stick to free water. Singapore's tap water is perfectly safe to drink. Bring a reusable bottle and fill it up at public fountains or your accommodation to avoid paying $3 SGD for bottled water at convenience stores.
Prioritize free attractions. Spend your time at the Gardens by the Bay (the outdoor gardens are free), the Singapore Botanic Gardens, the Henderson Waves bridge, or the free light shows at Marina Bay Sands and the Supertree Grove.

Is alcohol expensive in Singapore?: Yes. A single pint of beer can cost $15-20 SGD at a bar. If you want to drink, buy it at a supermarket (7-Eleven or FairPrice) and drink it in your room, though even then, it is heavily taxed.
Are there free things to do at night?: Yes. The Spectra light show at Marina Bay Sands and the Garden Rhapsody light show at the Supertree Grove are both free and happen every night.
Should I buy a SIM card?: If you want to save, don't. Use free public Wi-Fi available at almost all malls, MRT stations, and public buildings. If you need data, get an eSim like Airalo for about $10 USD.