I reside in India, but will be going to Sweden for business purposes. Can I visit London by applying for a visa from Sweden?
You can apply for a UK visa from any location where there is a visa application centre (VAC), it does not have to be from your country of residence, so yes, you can apply from Sweden. A Standard Visitor visa costs £93 and typically takes up to 3 weeks to process (it can take longer in some cases) https://www.gov.uk/standard-visitor-visa
It should be possible to complete the application online in India and book a biometric appointment at a VAC in Sweden, however if you’re not planning to be in Sweden for at least 3 weeks afterwards there’s a risk you won’t get the decision, and thus your passport, back in time. There may be a ‘keep my passport’ option when you apply that would solve this, although there’s still a risk that you wouldn’t get the decision in time.