Hmm, if Spain joins, the Brits could be in some real danger in the Med. If Spain is in then Gibraltar is threatened. On the other hand, Spain is situated prett precariously. The Spanish colonies will be gone pretty soon, and if/when the Americans show up, Spain is probably going to take the place of Italy as the "soft underbelly".
edit: and yes, Spain would suffer enormoudly from the lack of imports, especially considering as the situation the country was in without joining the Axis was not exactly rosy, following years of civil war.
Sweden joining the Axis, especially in that timeframe, seems unlikely to say the least. Sweden is in no shape militarily to join in any offensive war, has been at peace since the Napoleonic wars, has a policy of neutrality, has a democratically elected social-democratic prime minister, and is somewhat insured from a German attack by the ability to destroy the iron mines in the north that are supplying Germany's war effort. If you want Sweden in the Axis, you'd be better off going with Sweden joining Finland in the Winter War.
If Sweden were to join the axis, expect no changes other than maybe a few token soldiers on the eastern front, most likely helping the Finns in the continuation war. Sweden most likely won't get invaded by the allies, seeing as how the Red Army stopped in Finland and didn't occupy it, and Norway wasn't liberated by force.
I don't know enough about Turkey at the time to say, but I don't think they ever showed any inclination to join the Axis, being closer to the USSR. If they joined, and later wound up fighting the USSR instead of refusing to fight the USSR, the Germans could station troops in eastern Turkey prior to an attack toward the Baku oilfields. But how many troops would be needed, and what other part of the front would the Germans take them from? Would this slow other parts of the advance?