"Baso" applies to all types of drinking glasses, be it made of glass, plastic, metal, wood, or paper (paper cup).
If you'd like to ask for a glass of water, you can say:
"Pwedeng (pwede + na) makahingî ng isáng basong tubig?" = Could I ask for a glass of water, please? OR "Pwede pong (po + na) makahingî ng isáng basong tubig?" (same meaning, just more respectful)
"Pwede pong makahingi ..." would be respectful and is appropriate if you're a guest in someone's house, especially if you're addressing a person who you think is at least about your age.
"Pwedeng makahingi..." is the norm in restaurants. Even without the "pong", it will still sound respectful for as long as you don't sound demanding.
If you're asking for water for your group:
"Pwede kamíng makahingî ng tubig? = Could we ask for water, please? (The "ng" in "pwedeng" above now goes to the end of "kami" = kaming (kami + na). - (in a restaurant)
"Pwede po kamíng makahingî ng tubig? (More respectful. The "ng" in "pong" above now goes with "kami" => "kaming") (as a guest in someone's home)
There's a popular Filipino folk dance called "Pandanggo sa Ilaw" (Fandango with lights) and a similar one called "Oasíoas" (o-wa-si-was). I mentioned these because crystal glasses with lighted candles inside are used in these dances. Whenever possible also, the lights are turned off towards the end of the dance and the effect can be magical.
"Oasioas" is an old regional spelling of the Tagalog word "iwasiwas". It is not a commonly used word. It means to wave (like a flag) or to brandish (like a sword). "Iwagáywáy" is more often used now than "iwasiwas".
Pandanggo sa Ilaw - Oasioas: https://www.youtube.com/watch?v=wMmltK8VGTI