I shall give a reference after this simple note:

When students prepare,e.g., cyclohexene from cyclohexanol, they confirm the formation of the alkene by 2 tests (Br2 in CCl4 or in CH2Cl2 test & cold aqueous solution of KMnO4 called Bayer's test). The first test is more reliable than the second test.

That there is little alkaline with KMnO4 is better than using strong acidic medium (which causes cleavage on the double bond site).

In the test, the purple oxidizing agent (KMnO4) undergoes reduction (Mn7+ becomes Mn2+ in MnO2 which is a dark brown precipitate). When a chemist adds one or two drops of H2SO4, the aim is to speed up the test reaction to observe the color change from purple to dark brown. The basic salt NaHSO3 is well-known as a reducing agent and its function is to to enhance milder conditions by acting against excesses of both KMnO4 & H2SO4 . This reference is helpful:

https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Alkenes/Reactivity_of_Alkenes/Oxidation_of_Alkenes_with_Potassium_Manganate