I believe it is still called a Gin and Tonic, because the ratio of ingredients
remain the same. You just reduce them equally to fit in the glass.
http://www.webtender.com/db/drink/1683
Tanqueray and Tonic
2/3 Gin (Tanqueray)
1/3 Tonic water
1 slice Lime
Mixing instructions: Add ice to glass. Fill 2/3 of the way up with Tanqueray
Gin, and the remaining 1/3 with tonic water. Add lime.
-------------http://www.webtender.com/db/drink/404
Gin And Tonic
2 oz Gin
5 oz Tonic water
1 Lime wedge
Mixing instructions: Pour the gin and the tonic water into a highball glass
almost filled with ice cubes. Stir well. Garnish with the lime wedge.