The story of Lot is told in Genesis 19. In that story, the nature of Sodom's sin is not specified.
The Quran tells the same story (more or less), but it is clear about the nature of Sodom's sin. It was homosexuality ("men lusting after other men instead of women").
And Lot! (Remember) when he said unto his folk: Will ye commit abomination such as no creature ever did before you? Lo! ye come with lust unto men instead of women. Nay, but ye are wanton folk. Quran 7:80-1
What! Of all creatures do ye come unto the males, And leave the wives your Lord created for you? Nay, but ye are froward folk. 26:165-6
And Lot! when he said unto his folk: Will ye commit abomination knowingly? Must ye needs lust after men instead of women? Nay, but ye are folk who act senselessly. 27:54-55
And Lot! (Remember) when he said unto his folk: Lo! ye commit lewdness such as no creature did before you. For come ye not in unto males. 29:28-29
